1. Introduction
1.1
How it works
The
FZW
is a high-precision device that measures laser wavelengths
using
a
set
of
Fizeau
interferometers.
A
Fizeau
interferometer
is
formed by two planar surfaces with a small wedge angle between
them, which generates spatially-varying interference fringes as the
optical path length changes (Fig. 1.1).
Both the fringe spacing and
phase of the resulting interference pattern are related to the wave-
length of the incident light, so analysing their structure allows pre-
cise determination of the laser wavelength.
Figure 1.1:
Collimated monochromatic laser light and Fizeau etalons cre-
ate interference patterns on an imaging detector. The wavelength is calcu-
lated by combining measurements of the fringes from four different etalons.
A
rough
estimate
of
the
wavelength
is
obtained
directly
from
the
fringe
spacing,
to
an
absolute
accuracy
of
one
part
in
100.
This
initial estimate is then improved by the phase of the fringe pattern.
Multiple etalons with different free-spectral ranges (
FSRs
) are used
to refine the wavelength measurement without sacrificing absolute
accuracy. The
MOGL
abs
FZW
uses four such stages, with the
FSR
of
the final etalon being 7.5 GHz.
This enables the wavelength to be
determined to an absolute accuracy of one part in 10
7
.
1
Summary of Contents for FSW4
Page 1: ...Fizeau Wavemeter and Fibre Switcher FZW600 FSM2 FSW4 FSW8 Firmware v0 9 5 mogfzw v1 4 5 ...
Page 36: ...30 Chapter 5 PID locking ...
Page 50: ...44 Appendix A Specifications ...
Page 60: ...54 Appendix C Command language ...
Page 62: ...56 Appendix D Errors and troubleshooting ...
Page 67: ...F Dimensions and PCB 83 120 146 32 9 30V PID TRIG FSW Figure F 1 FZW chassis dimensions 61 ...
Page 68: ...62 Appendix F Dimensions and PCB 146 33 37 120 18 Figure F 2 FSW fibre switch dimensions ...
Page 71: ......